This invention relates to a strainer of the type to be used for the filtration of liquids, particularly for attachment to the free end of a suction pipe inserted into a gasoline tank so as to prevent said suction pipe from admitting impurities.
Strainers of this type developed heretofore have generally consisted of a cylindrical metallic frame and a metal net wrapped around the frame or of a cylindrical plastic frame having a plastic net stretched inside said frame. A strainer having a metallic structure is difficult to assemble and inevitably proves to be expensive. Such a metallic strainer does not permit easy replacement because the required union between the suction pipe and the strainer body is generally obtained by soldering. Thus it cannot be mass produced. A strainer having a plastic structure is generally of such a configuration that the top plate and bottom plate cannot be molded in a unitary form with the cylindrical strainer frame. Other strainer structures which are difficult to use in separating the suction pipe from the strainer body include: structures where the suction pipe is fastened to the strainer body by use of adhesive, and structures where the opening formed in the strainer body to permit insertion of the suction pipe and the portion of the suction pipe brought into engagement therewith are provided respectively with a protuberance and a matching groove. Those strainers, having structures such as those described above, have a disadvantage in that the strainer body and the suction pipe cannot be connected stably with each other unless the diameter of the through hole formed in the top plate of the strainer and the outside diameter of the suction pipe are perfectly equal to each other otherwise, because of a gap formed therebetween, the strainer body permits inflow of impurities.
A primary object of the present invention is to provide a strainer capable of being easily connected to a matching suction pipe with perfect airtightness while also being freely detachable therefrom.
Another object of this invention is to provide a strainer easily shaped in a unitary structure by injection molding of a plastic.